1. Technical Field
The invention relates to an image forming zoom lens for use in an imaging device, such as CCD and a camera tube, or in a camera using a silver halide film; and relates to a projection zoom lens for use in a projection television and. More particularly, the invention relates to a projection zoom lens for use in a projection display device using a liquid crystal display device or DMD (digital micromirror device), and a projection display device using the same.
2. Description of the Related Art
JP 2002-148516 A (corresponding to U.S. Pat. No. 6,542,311) discloses a zoom lens having the five-group configuration. This zoom lens has a power arrangement of negative, positive, positive, negative and positive sequentially from the magnification side. Although JP 2002-148516 A uses only glass spherical lenses but uses no aspherical lens, JP 2002-148156 A achieves miniaturization. Also, this zoom lens is configured so that a telecentric property and a proper back focus can be obtained on the reduction side. JP 2000-111797 A (one of basic Japanese patent applications of U.S. Pat. No. 6,285,509) discloses another zoom lens having the five-group configuration and having the similar power arrangements. The zoom lens disclosed in JP 2000-111797 A can maintain the telecentric property over a full variable power range.
However, the zoom lens disclosed in JP 2002-148516 A still leaves room for improvement as to a distortion correction and has not a sufficient brightness. Also, in JP 2000-111797 A, an aspherical lens is provided in front of the first lens of the first lens group, and a plastic lens is used as the first lens for the purpose of a molding easiness and a cost reduction. In this case, from the viewpoint of the weather resistance, it is not preferable to make the first lens, which is to be susceptible to damage, of plastic.